VSEPR Theory Overview
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Questions and Answers

What are the steps to draw a Lewis Structure for a molecule?

  • Determine the molecular mass, draw the shape, and add valence electrons.
  • Decide on bonded atoms, count all valence electrons, and complete octets. (correct)
  • Count the number of protons and electrons, then create bonds.
  • Connect atoms based on charge, then arrange electrons evenly.

What type of electron pair has more spatial occupancy in a molecular structure?

  • Lone pairs (correct)
  • Single bonding pairs
  • Pie bonds
  • Double bonding pairs

Which statement correctly describes VSEPR theory?

  • It states that ionic compounds have directional bonding.
  • It provides a method to calculate molecular speeds.
  • It suggests all compounds have the same geometric structure.
  • It explains that molecular shapes depend on atom arrangements and electron pairs. (correct)

What is true regarding bonding pairs and lone pairs in a molecule?

<p>Bonding pairs have less spatial occupancy compared to lone pairs. (A)</p> Signup and view all the answers

What best explains why the shape of a molecule is significant?

<p>It influences the physical and chemical properties of the substance. (D)</p> Signup and view all the answers

Which of the following statements about electron pairs is accurate?

<p>Single bonds are formed by one electron pair. (C)</p> Signup and view all the answers

What is one of the key distinctions between ionic and covalent bonding?

<p>Covalent bonding involves the sharing of electrons. (C)</p> Signup and view all the answers

What does VSEPR stand for?

<p>Valence Shell Electron Pair Repulsion (D)</p> Signup and view all the answers

Which type of repulsion is considered the strongest according to VSEPR theory?

<p>Lone pair-lone pair (LP-LP) repulsion (A)</p> Signup and view all the answers

What is the bond angle in a molecule with a tetrahedral shape?

<p>109.5° (D)</p> Signup and view all the answers

In determining the VSEPR shape of a molecule, what is the first step?

<p>Draw the Lewis structure (C)</p> Signup and view all the answers

Which molecular shape corresponds to a central atom with only 2 bonding pairs?

<p>Linear (D)</p> Signup and view all the answers

If a central atom is surrounded by four bonding pairs, what shape does it take according to VSEPR?

<p>Tetrahedral (D)</p> Signup and view all the answers

How should double bonds be counted when determining the electron domains in a molecule?

<p>Each double bond counts as one electron pair (D)</p> Signup and view all the answers

In a molecule with a central atom having three bonding pairs, what structure is formed?

<p>Triangular (Trigonal) Planar (C)</p> Signup and view all the answers

What shape do atoms form when arranged in a triangular bipyramidal configuration?

<p>Trigonal bipyramidal (C)</p> Signup and view all the answers

What is the bond angle between the atoms in the base of the triangular bipyramidal molecule?

<p>120° (C)</p> Signup and view all the answers

Which type of bond occurs when there is an equal sharing of electrons between nonmetal atoms?

<p>Nonpolar covalent bond (A)</p> Signup and view all the answers

In molecules with 6 pairs of bonding pairs, what geometric shape is formed?

<p>Regular octahedron (A)</p> Signup and view all the answers

What is the maximum electronegativity difference that characterizes polar covalent bonds?

<p>1.7 (A)</p> Signup and view all the answers

What is the bond angle in a molecule shaped like a tetrahedron when there are only 2 bonding pairs?

<p>104.5° (B)</p> Signup and view all the answers

Which of the following molecules is an example of a nonpolar molecule due to symmetrical cancellation of dipoles?

<p>CO (B)</p> Signup and view all the answers

Which element has the highest electronegativity based on the given content?

<p>Fluorine (A)</p> Signup and view all the answers

Which of the following best describes a polar molecule?

<p>The dipoles from individual bonds do not cancel each other out. (B)</p> Signup and view all the answers

Which of the following statements about electronegativity is true?

<p>It indicates the attraction of an atom for shared electrons. (D)</p> Signup and view all the answers

What shape is adapted by a molecule with 2 bonding pairs and 2 non-bonding pairs of electrons?

<p>Bent or V-shape (D)</p> Signup and view all the answers

In which scenario would a polar covalent bond most likely be formed?

<p>Between nonmetal atoms with a significant difference in electronegativity (A)</p> Signup and view all the answers

Which of the following pairs of atoms is NOT likely to form a nonpolar covalent bond?

<p>O - H (D)</p> Signup and view all the answers

How does the bond angle change with each pair of non-bonding electrons?

<p>Decreases by 2.5° (C)</p> Signup and view all the answers

What type of bond exists between the chlorine atom and carbon in the Cl-C bond?

<p>Polar covalent bond (D)</p> Signup and view all the answers

Which of the following molecules would be classified as polar due to its shape?

<p>H2O (A)</p> Signup and view all the answers

Flashcards

VSEPR Theory

Predicts the three-dimensional shape of molecules based on the arrangement of electron pairs around a central atom.

Electron Group

A group of atoms bonded to a central atom.

Bonding Pair

A pair of electrons that are shared between two atoms, forming a covalent bond.

Lone Pair

A pair of electrons that are not involved in bonding and reside around the central atom.

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Lone Pair-Lone Pair (LP-LP) Repulsion

The repulsion between two lone pairs of electrons.

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Lone Pair-Bonding Pair (LP-BP) Repulsion

The repulsion between a lone pair of electrons and a bonding pair of electrons.

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Bonding Pair-Bonding Pair (BP-BP) Repulsion

The repulsion between two bonding pairs of electrons.

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Molecular Shape

The arrangement of electron groups around the central atom dictates the shape of the molecule.

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Trigonal Bipyramidal

A molecular shape with 5 atoms arranged such that the central atom has three atoms in a triangular plane and two atoms above and below the plane.

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Octahedral

A molecular shape with 6 atoms arranged such that the central atom is surrounded by 4 atoms in a square plane and two atoms above and below the plane.

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Bent/V-shape

A molecular shape with two atoms bonded to a central atom, often with lone pairs of electrons around the central atom, resulting in a V-shape.

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Electronegativity

A measure of an atom's ability to attract electrons towards itself in a covalent bond.

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Polar Covalent Bond

A covalent bond where the electrons are shared unequally between two atoms due to a difference in electronegativity.

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Polar Molecule

A molecule that has a separation of positive and negative charges, due to uneven sharing of electrons in its bonds.

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Electron Pair Repulsion

The force of repulsion between electron pairs around a central atom. Lone pair-lone pair repulsion is the strongest, followed by lone pair-bonding pair, and then bonding pair-bonding pair.

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Electron Domain

A region in space around a central atom where an electron pair is located.

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Linear Shape

The shape of a molecule with a central atom surrounded by two bonding pairs. The bond angle is 180 degrees.

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Trigonal Planar Shape

The shape of a molecule with a central atom surrounded by three bonding pairs. The bond angles are 120 degrees.

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Tetrahedral Shape

The shape of a molecule with a central atom surrounded by four bonding pairs. The bond angles are 109.5 degrees.

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Molecules with Incomplete Octet: 2 Bonding Pairs

A molecule that has a central atom with only two bonding pairs, resulting in a linear shape.

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Molecules with Incomplete Octet: 3 Bonding Pairs

A molecule that has a central atom with only three bonding pairs, resulting in a trigonal planar shape.

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Nonpolar Covalent Bond

A bond between two nonmetals with an equal or nearly equal sharing of electrons.

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Nonpolar Molecule

A molecule where all bonds are nonpolar, or where polar bonds cancel each other out due to symmetrical arrangement.

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Cancellation of Polar Bonds

Polar bonds within a molecule can cancel each other out if the molecule has a symmetrical shape.

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Dipole Moment

The unequal sharing of electrons in a polar covalent bond creates a partial positive and a partial negative charge on the atoms.

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Molecular Geometry (Shape) and Polarity

The shape of a molecule determines whether polar bonds cancel each other out, influencing its polarity.

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Study Notes

VSEPR Theory

  • VSEPR stands for Valence Shell Electron Pair Repulsion
  • The theory explains the shapes of molecules
  • Molecule shapes are determined by the repulsion between valence electron pairs
  • Electron pairs (bonding and lone pairs) repel each other, trying to get as far apart as possible
  • Shapes are predicted based on the number of bonding and lone pairs around the central atom

Steps to Determine VSEPR Shape

  • Draw the Lewis structure of the molecule
  • Determine the central atom (the least electronegative)
  • Determine the number of bonding pairs
  • Determine the number of lone pairs
  • Consult the VSEPR chart to find the shape

Molecules with Incomplete Octet

  • Molecules with 2 bonding pairs are linear with a bond angle of 180°
  • Molecules with 3 bonding pairs are triangular (trigonal planar) with bond angles of 120°
  • Examples include BeFâ‚‚ and BF₃

Molecules with Four Bonding Pairs

  • If the central atom has four bonding pairs, the shape is tetrahedral with a bond angle of 109.5°
  • Example: CCIâ‚„

Molecules with Five Bonding Pairs

  • With five bonding pairs, the shape is trigonal bipyramidal
  • Bond angles are 120° and 90°
  • Example: PFâ‚…

Molecules with Six Bonding Pairs

  • With six bonding pairs, the shape is octahedral
  • Bond angles are all 90°
  • Example: SF₆

Molecules with Two Bonding Pairs and Two Non-bonding Pairs

  • Shape is bent or V-shaped with a bond angle of 104.5°
  • Example: Hâ‚‚O

Polarity of Molecules

  • Nonpolar molecules:
    • All bonds are nonpolar, or
    • Polar bonds (dipoles) cancel each other out.
    • Examples include Hâ‚‚, Clâ‚‚, CHâ‚„
  • Polar molecules:
    • Dipoles do not cancel.
    • Shape of the molecule (bent, trigonal pyramidal) determines if dipoles cancel.
    • Examples include HCl, Hâ‚‚O, NH₃

Electronegativity

  • Indicates the attraction of an atom for shared electrons
  • Increases from left to right across a period on the periodic table
  • High for nonmetals (with fluorine being the highest)
  • Low for metals

Electronegativity and Bond Polarity

  • Nonpolar covalent bonds:
    • Occurs between nonmetals
    • Equal or almost equal sharing of electrons
    • Difference in electronegativity is less than 0.4
  • Polar covalent bonds:
    • Unequal sharing of electrons
    • Difference in electronegativity is between 0.4 and 1.7
  • Ionic bonds:
    • Electron transfer
    • Difference in electronegativity is greater than 1.7

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VSEPR Theory PDF

Description

Explore the Valence Shell Electron Pair Repulsion (VSEPR) theory and how it predicts molecular shapes. This quiz provides key steps to determine the geometry of molecules, including examples and shapes based on bonding and lone pairs. Perfect for students looking to grasp molecule structure concepts.

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